1. Field of the Invention
The invention relates to device for controlling the contact pressure of a textile coil on a support or driving cylinder, wherein the coil is supported by an articulatingly suspended coil holder having a lever fastened thereon and forming part of a spring-loaded toggle-joint assembly.
2. Description of the Prior Art
In various machines for the production, processing or testing of yarns or threads, such as winding machines, spinning machines or texturizing machines, for example, the thread or yarn is wound on a universal or cross-wound coil or cheese winding device. The coil or bobbin is braced or supported by a conical or cylindrical roller which often also assumes the task of driving the coil or bobbin.
The contact area between the roller or cylinder and the textile coil or bobbin is subjected to the application of forces which depend upon the volume and weight of the bobbin or coil, the weight of the coil holder, and the angular position of the coil holder relative to the cylinder or roller. The weight of the coil increases as the square of the coil diameter. This results in an undesirable increase in the contact pressure between the coil and the cylinder or roller as the diameter of the textile coil increases.
Previously known devices have provided the coil holder with a lever which is part of a spring-loaded toggle-joint assembly. In the fully extended or stretched position of the toggle joint, the spring exerts no torque on the coil holder when the coil diameter is not too small. If the coil diameter is small, however, the toggle joint is deflected to one side so that the spring exerts a torque on the coil holder which acts in a direction tending to increase the contact pressure. With increasing coil diameter, this torque becomes smaller and finally zero, whereupon the toggle joint is deflected to the other side so that the spring then exerts a torque which acts on the coil holder in a direction tending toward decreasing the contact pressure, the last mentioned torque becoming larger with increasing coil diameter.
Through a suitable choice of the joint configuration, the joint dimensions and the spring characteristic, a resulting contact pressure can be attained which is approximately constant or becomes smaller with increasing coil diameter. It is difficult, however, to vary the contact pressure exactly in accordance with a given build-up or formation of the textile coil being wound.
Since the contact pressure has a great influence or effect upon the coil density and the firmness or compactness of the coil, attempts have been made to adapt or accommodate the contact pressure to the further processing of the textile coil by changing the weight of the coil holder or the force of the spring. Dyeing coils are thus made with a contact pressure that is light and as constant as possible. On the other hand, coils from which good thread withdrawal characteristics are expected, are produced with a very high contact pressure at the start of the winding operation and with decreasing contact pressure as the coil diameter increases, the decrease in the contact pressure preventing the windings from bulging or billowing out at the end faces of the textile coil.
Heretofore known devices of this general type and their limited possibilities of adjustment have not been able to meet these different requirements to the demanded extent and with the desired characteristics.